Particularly in an airplane, it is essential to be aware at all times of the quantity, and above all the residual weight, of fuel contained in the tank or tanks.
At present, use is made above all of a system comprising a capacitive gauge, or more frequently a plurality of gauges distributed in the or each tank, and suitable for delivering an electrical signal representative of the length of the gauge that is immersed in fuel. Thus, each gauge enables the level of the free surface of the fuel to be measured. The gauges are connected to a computer which also receives signals coming from other sensors, giving information concerning the specific gravity, the dielectric constant, and/or the temperature of the fuel, thereby making it possible to determine the residual weight with high accuracy.